A MFD (Multi-Function Device) is a rendering device or office machine which incorporates the functionality of multiple devices in a single apparatus or system so as to offer a smaller footprint in a home or small business setting, or in some cases, to provide centralized document management/distribution/production in the context of, for example, a large-office setting. A typical MFD may provide a combination of some or all of the following capabilities: printer, scanner, photocopier, fax machine, e-mail capability, and so forth. Networked MFDs (Multi-Function Devices) generally interact with an assemblage of varying rendering devices, client computers, servers, and other components that are connected to and communicate over a network.
Multi-function office reprographics devices utilize low-cost scanners in order to deliver a more economical solution. Unfortunately, such low-cost scanners do not provide a high-speed image processing throughput rate at a native image resolution, which is often expected by users and customers. For example, candidate low-cost scanners do not generate the desired 50 ppm processing rates when scanning at the native 600×600 spi resolution needed for the MFD products. Table 1 below summarizes an example benchmark study of applicable low-cost contact image sensors (CIS) for a competitive, low-cost MFD product under consideration. Note that such data is not considered a limiting feature of the disclosed embodiments, but is shown for exemplary purposes only. As indicated below, none of the candidate vendors met the 50 ppm product goal criteria at the 600×600 spi input scan resolution, whereas vendors “A” and “B” met the 50 ppm throughput rate but at a lower 600×300 spi resolution.
TABLE 1A4 Document MFDThroughput Speed (PPM)ProductResolutionVendor “A”Vendor “B”Vendor “C”Goal600 × 300 SPI50 PPM76 PPMNot Available50 PPM600 × 600 SPI25 PPM38 PPM20 PPM
Conventionally, error diffusion has been employed in a MFD copy-path to render a print-ready bitmap from a scanned monochrome/color image, since the error diffusion inherent properties provide favorable processing features without generating imaging/print artifacts. In general, processing an image via error diffusion generates an output image at the same input resolution, albeit with a lower bit-depth (i.e. 8 bpp→1 bpp). One alternative to processing the lower resolution image is to simply replicate/interpolate either an input contone image prior to rendering, or replicate a rendered binary output in order to generate the higher-resolution print-ready bitmap.
FIG. 1 represents a schematic diagram illustrating a snippet of 600×300 scan lines 10, with pixels 15 representing the lower-resolution scanned input image and the pixels 20 representing the interpolated or replicated scan lines. Unfortunately, either doubling the input 8 bpp contone image or 1 bpp binary output bitmap has throughput and image-quality disadvantages, respectively. Both techniques offer disadvantages with respect to the image-quality and/or reduced document throughput rates.
Based on the foregoing, it is believed that a need exists for an improved method and system for processing a low resolution image via a low resolution error diffusion algorithm, as will be described in greater detail herein.